Systems and methods for digital processing of satellite communications data

ABSTRACT

A digital payload for processing a sub-band spectrum received on an uplink beam at a communications satellite includes a digital channelizer, a digital switch matrix and a digital combiner. The digital channelizer divides the sub-band spectrum into a plurality of frequency slices that can be routed by the digital switch matrix to any of a number of receiving ports. A digital combiner receives the frequency slices and re-assembles them to form one or more output sub-bands for transmission on an output beam of the communications satellite. The digital payload may also include an embeddable digital regeneration module configured to demodulate some or all of the sub-band spectrum to extract a digital bitstream therefrom. The digital bitstream may be processed to implement code-based multiplexing, switching, access control, and other features.

PRIORITY CLAIM

[0001] This application claims priority of U.S. Provisional ApplicationSerial No. 60/443,517 filed on Jan. 28, 2003. This application alsoclaims priority of U.S. Provisional Application Serial No. 60/443,664filed on Jan. 29, 2003. Both of these disclosures are incorporatedherein by reference in their entirety.

TECHNICAL FIELD

[0002] The present invention generally relates to satellites, and moreparticularly relates to a digital architecture for satellites.

BACKGROUND

[0003] Satellites have become invaluable tools in such diverse fields asnavigation, communications, environmental monitoring, weatherforecasting, broadcasting and the like. Hundreds of man-made satellitesnow orbit the earth, and each year many more are launched from variousnations around the world. Moreover, many homes, businesses andgovernment organizations now use satellite systems on a daily basis forentertainment, communications, information gathering and other purposes.

[0004] A typical modem satellite has a metal or composite frame thathouses a power source (e.g. one or more batteries, solar cells and/orthe like) and various electronic components, as well as one or moreantennas. The components generally include one or more “transponders”,which are clusters containing one or more radio receivers, frequencytranslators and transmitters. The total bandwidth of the satellite isprovided by the number of transponders, each of which may have a typicalbandwidth of 30-70 MHz or so. One type of commercially-availablesatellite, for example, has a total available bandwidth of 3,528 MHzdivided across forty-five C-band and sixteen Ku-band transponders. Thesetransponders are collectively referred to as “the payload” of thesatellite.

[0005] As shown in FIG. 1, a typical analog transponded communicationspayload receives multiple uplink beams from the earth or anothersatellite via an uplink antenna. Each of the received beams is amplifiedwith a low noise amplifier (LNA) and down-converted (D/C) for furtherprocessing. The down-converted beams can then be switched, multiplexed(MUX) or otherwise routed and combined prior to upconversion andre-transmission on a downlink beam to the earth or another satellite.

[0006] Although some analog transponded satellites may include limitedswitching and multiplexing functionality, these features are restricted,with switching limited to point-to-point mapping of entire uplinkantenna beams to particular downlink antenna beams. This leads to majorinefficiencies in the use of satellite bandwidth. A satellite customertypically purchases a “transponder”, or dedicated block of bandwidth ona satellite, for a period of one year or more. Transponder bandwidthsare typically fixed in the satellite during design (e.g. at 33, 50, 70MHz, etc.) and are not finely adjustable after the satellite isconstructed. Each transponder provides a connection with dedicatedbandwidth and power between two points on the earth (point-to-point), orbetween one point and broad geographic areas (broadcast). While thisarrangement is relatively flexible with respect to the type of signalscarried, there are major disadvantages in terms of bandwidth efficiencyand transmit power control. Should a satellite customer need slightlymore bandwidth than that provided by the transponder, for example, thesatellite customer must generally purchase another “transponder-sized”bandwidth segment of 33-70 MHz. Further, if a satellite customer doesnot use all of its transponder bandwidth, this excess capacity remainsunused, wasting a limited and valuable commodity. While some customershave attempted to address this inefficiency by sub-allocating purchasedtransponder bandwidth to other end users via dedicated terrestrialterminal equipment and extensive special arrangements, sub-allocationtypically requires the satellite customer to trust the end users tocontrol their own power and bandwidth usage because no positive controlis available to regulate bandwidth and power consumption onboard thesatellite. In addition, satellite “pirates” frequently “piggyback”signals onto unused transponder bandwidth, robbing transmit power anddegrading communication link performance for legitimate users. Due inlarge part to these inefficiencies and other factors, the cost ofsatellite communications remains relatively high compared to terrestrialcommunications systems, thereby limiting the widespread adoption ofsatellite communications for many applications.

[0007] Satellite payloads have evolved more recently to take advantageof digital technologies for enhanced flexibility and control. Digitalsatellite payloads generally function in either a channelized manner ora regenerative manner. In the former case, a digital payload simulatestraditional fixed analog transponders, but adds the ability to finelydivide, control and monitor bandwidth and power allocation onboard thesatellite. Digital transponded payloads normally have the ability toperform switching of inputs to outputs in a highly flexible manner,enabling them to act as virtual “telephone exchanges”, where a requestfor a channel with specific bandwidth/power and antenna characteristicsis made, the channel is set up, used, then disconnected. This “circuitswitched” capability ensures that only the bandwidth, transmit power andcoverage needed is provided, and only when it is needed. Sincetransponded channels are merely repeated signals, without anymodification, transponder payloads can carry any type of signal withoutregard to format or modulation mode. Unlike transponded payloads,regenerative payloads perform demodulation and remodulation of uplinkedsignals, recovering and processing not just the user signal, but alsothe user data embedded within the signal, enabling the payload to actupon it in a desired manner. Embedded data is most often used forautonomous routing in packet based systems and for security functions,as in many government satellites, or both. In particular, errordetection and correction can be performed on demodulated data before itis retransmitted, thereby allowing regenerative satellite payloads togenerally have better link performance than transponded payloads. Thesecharacteristics and others make regenerative payloads the most efficientavailable in terms of control, bandwidth and power use. Regenerativesystems, however, are commonly built to process a single set of signaland data formats that is fixed at design time. Such systems do nottypically provide universal signal compatibility as may be availablefrom transponded payload possesses.

[0008] As satellite payload evolution continues, satellite customers areprogressing from analog transponded to digital transponded to digitalregenerative approaches to extract the maximum revenue bearing bandwidthand power from spectrum allocations fixed by law. Digital transpondersystems may be relatively easily made to be backward compatible withanalog transponder systems since neither system provides onboard dataprocessing. Regenerative systems are generally not backward compatible,however, due to their requirements for specific signal and data types.While the transition from analog transponded payloads to much moreefficient digital transponded payloads is clear, the path to provideeven more efficient regenerative payload capability without droppinglegacy system users or requiring the satellite to carry significantlymore processing electronics has been difficult. To avoid loss ofoperation and to provide continuous revenue flow, existing satellitecustomers generally desire to transition transponded end users toregenerative services in a gradual manner, over the many-year life spanof an expensive satellite asset.

[0009] It is therefore desirable to improve the flexibility andfunctionality of satellite payloads used in data communications incommercial and/or government settings. It is further desirable toprovide a satellite payload capable of simultaneously mixing transpondedand regenerative modes in a hardware efficient payload, and to providein-service programmability for regenerative signal and data formats.Furthermore, other desirable features and characteristics will becomeapparent from the subsequent detailed description and the appendedclaims, taken in conjunction with the accompanying drawings and thisbackground of the invention.

BRIEF SUMMARY

[0010] According to various exemplary embodiments, both digitaltransponded and digital regenerative functions are provided within anall-digital satellite payload. By combining transponded and regenerativefunctions into a common digital platform, numerous efficiencies of scaleare realized, and the overall efficiency and functionality of thesatellite is dramatically improved.

[0011] In one embodiment, a digital payload for processing a sub-bandspectrum received on an uplink beam at a communications satelliteincludes a digital channelizer, a digital switch matrix and a digitalcombiner. The digital channelizer divides the sub-band spectrum into aplurality of frequency slices that can be routed by the digital switchmatrix to any of a number of receiving ports. A digital combinerreceives the frequency slices and re-assembles them to form one or moreoutput sub-bands for transmission on an output beam of thecommunications satellite. The digital payload may also include anembedded digital regeneration module configured to demodulate some orall of the sub-band spectrum to extract a digital bitstream therefrom.The digital bitstream may be processed before, during and/or after therouting function to implement code-based switching, multiplexing, accesscontrol, output linearization and other features.

[0012] In another embodiment, a method of processing a sub-band spectrumreceived on an uplink beam at a digital payload for a communicationssatellite suitably includes the steps of digitally dividing the sub-bandspectrum into frequency slices and routing each of the frequency slicesbetween a number of receiving ports. Some or all of the frequency slicesmay be digitally demodulated, processed and/or remodulated before,during and/or after routing, as appropriate. The routed and/or processedfrequency slices are then digitally re-assembled to thereby form outputsub-bands for transmission on one or more output beams of thecommunications satellite.

[0013] Other aspects variously relate to satellite components, systemsand methods. The concepts set forth further herein allow new techniquesfor commercializing satellite resources, and several new business modelswithin the satellite field. These and other aspects of various exemplaryembodiments are set forth in detail below.

BRIEF DESCRIPTION OF THE DRAWINGS

[0014] The present invention will hereinafter be described inconjunction with the following drawing figures, wherein like numeralsdenote like elements, and

[0015]FIG. 1 is a block diagram of an exemplary prior art satellitepayload.

[0016]FIG. 2 is a block diagram of an exemplary satellite having aflexible transponder payload;

[0017]FIG. 3 is a block diagram of an exemplary digital satellitepayload;

[0018]FIG. 4 is a perspective view of an exemplary embodiment of apacket processing digital payload;

[0019]FIG. 5 is a block diagram of an exemplary embodiment of apacket-processing digital payload;

[0020]FIG. 6 is a block diagram of an exemplary embodiment of amulti-slice digital payload;

[0021]FIG. 7 is a block diagram of an exemplary satellite having amodular data handling capability;

[0022]FIG. 8 is a block diagram of a satellite having an exemplaryall-digital payload;

[0023]FIG. 9 is a flowchart of an exemplary process for allocatingbandwidth in a digital satellite payload;

[0024]FIG. 10 is a flowchart of an exemplary process for allocatingsatellite resources; and

[0025]FIG. 11 is a conceptual diagram of an exemplary digital satelliteimplementation.

DETAILED DESCRIPTION

[0026] The following detailed description is exemplary in nature and isnot intended to limit the invention or the application and uses of theinvention. Furthermore, there is no intention to be bound by any theorypresented in the preceding background of the invention or the followingdetailed description.

[0027] According to various exemplary embodiments, a new digitalarchitecture provides a backward-compatible, broadband, switchedchannelizing digital payload for communications satellites. Because theamount of usable bandwidth available from a digital payload may be muchgreater than that provided by a corresponding analog payload, the costof bandwidth provided by the satellite is suitably reduced, therebyallowing reduced pricing to consumers and/or greater profit margins forbandwidth suppliers. Moreover, the integrated digital architectureallows for additional features and functionalities not previouslyavailable from other satellite payloads. As an example, variousembodiments allow payload resources (e.g. bandwidth, power, frequencyplans, antenna coverages, etc.) to be readily re-assigned during designor manufacturing of the satellite, or even on orbit, thereby greatlyimproving the flexibility of satellite designs. By allowing bandwidthand other resources to be adjusted on-orbit, the satellite can adapt tochanging consumer needs, thereby improving risk assessment of satelliteimplementations and enabling new marketing strategies for selling orreselling satellite bandwidth. These new strategies, in turn, providenew revenue streams for bandwidth providers while improving service toconsumers.

[0028] The various embodiments of the new architecture result in anall-digital satellite payload that is modular, reconfigurable andprogrammable. Although various embodiments of the new architecture aredescribed using terms such as “flexible transponder”, “modular datahandler” and “flexible satellite”, a wide array of equivalentembodiments may be formed using the general concepts set forth herein.

[0029] Turning now to the drawing figures and with reference now to FIG.2, an exemplary satellite payload 200 suitable for use with satellitecommunications is shown. In the embodiment shown in FIG. 2, payload 200suitably includes any number of input amplifiers 206A-n, optionaldownconverters (D/C) 208A-n, output amplifiers 210A-I, output switches212A-j and output multiplexers 214A-k that are arranged to interoperatewith a digital transponder unit 202 to provide digital processing ofinput beams 204A-n and to create output beams 216A-n that aretransmitted to a receiver at another satellite or at the earth's surfacevia a suitable antenna.

[0030] In operation, each input beam 204 is received via a suitableantenna (not shown in FIG. 2, but described more fully below). Each beammay be filtered to isolate an appropriate band of frequencies (i.e.“sub-bands” or “channels”) to be amplified by a low noise amplifier(LNA) or other input amplifier 206 to improve the strength of thereceived signal. The amplified sub-band is then downconverted from thereceived frequency to a suitable intermediate frequency (IF) for digitalprocessing. While the embodiment shown in FIG. 2 shows blockdown-conversions of 250-750 MHz sections of input bandwidth andswitching and filtering of 24-72 MHz channels, any other frequency bandsor ranges may be used in a wide array of alternate embodiments. Forexample, high-quality analog-to-digital converters may be used to sampleincoming sub-bands at rates as high as 550 MHz or greater, therebyreducing or eliminating the need to downconvert the amplified sub-bandsin many embodiments, as described more fully below. While conventionalsatellites most commonly use C and Ku band receive or transmitfrequencies the techniques described herein are extendable to UHF, L, S,and Ka band frequencies, as well as any other frequencies.

[0031] While conventional circuit switching architectures (e.g. thatshown in FIG. 1) simply switched and multiplexed entire channels betweeninput and output beams, various embodiments of digital transponder unit202 are capable of digitally dividing each sub-band into frequencyslices that can be separate switched, processed, routed and re-combinedin output sub-bands as described more fully below. To this end, thedigital transponder unit 202 replaces the input multiplexers andassociated switches, cabling, etc. shown in FIG. 1 while providingadditional functionality and efficiency not available in prior systems.This digital processing enables a number of new features that were notpreviously available, including reconstruction filtering of individualslices, traffic monitoring, transmit linearization, optimization, accesscontrol and the like. Moreover, the digital transponder 202 allows fortailoring of bandwidth and other resource allocations, thereby greatlyimproving the efficiency of payload 200. Bandwidth allocations on bothuplinks 204 and downlinks 216 can be adjusted in real time duringoperation, for example, to re-assign excess bandwidth to beams orsub-bands experiencing increased traffic demands. Variousimplementations of digital transponder units 202, components andassociated processing techniques are described below in greater detail.

[0032] The output sub-bands assembled by digital transponder unit 202are appropriately amplified with traveling-wave tube amplifiers (TWTA),solid-state power amplifiers (SSPA) or other suitable output amplifiers210. Although the particular output power varies from embodiment toembodiment according to such factors as the altitude above earth,transmit frequencies used, etc., typically output power of about 50W maybe used at C band frequencies and about 80-120W of power may be used atKu band. The outputs of some or all of the output amplifiers 210 may beswitched, multiplexed together at output mulitplexers 214, and thenre-transmitted through the transmit antennas to form output beams 216.Before multiplexing, optional variable power dividers (not shown inFIG. 1) may be used to allocate power to the various coverage areas asappropriate.

[0033]FIG. 3 shows one logical layout of an exemplary digital satellitesystem 300. With reference now to FIG. 3, an exemplary digitaltransponder unit 202 suitably communicates with any number of uplinkantennas 303A-N and any number of downlink antennas 315A-N to digitallyprocess uplink beams 204A-N and downlink beams 216A-N, respectively. Asdescribed above, uplink beams 204 may be downconverted in variousembodiments to allow sampling and A/D conversion at an appropriatefrequency, although the downconverters 208 may be eliminated orincorporated into transponder unit 202 in various alternate embodiments.

[0034] Uplink and downlink antennas 303 and 315 may be implemented withany conventional antennas used in satellite communications. In variousembodiments, antennas 303 and 315 are implemented with digital or analogbeamforming antennas having any number of independently-addressabletransmit/receive elements. Examples of such antennas include the variousspot beam dishes, multi-beam feed antennas, direct radiating arrayantennas and/or phased array antennas available from Boeing SatelliteSystems of Los Angeles, Calif. and others.

[0035] Digital transponder unit 202 suitably provides on-board switchingand sub-channel routing functionality. Because signals are digitallyrouted within transponder unit 202, variable sub-channel bandwidth cangenerally be provided with negligible degradation in signal quality.Channel widths, spacing and switching may be further programmed orotherwise modified on orbit, and some or all of the output sub-channelsmay be optionally configured with a commandable downlink level controlas appropriate. Further embodiments may also optimize uplinkconnectivity, as described more fully below (e.g. in conjunction withFIG. 10).

[0036] As shown in the exemplary embodiment of FIG. 3, digitaltransponder unit 202 suitably includes a digital channelizer module 302,a digital switch matrix 304, a digital combiner 306 and a digitalregeneration module 308. The various modules and sub-systems shown inFIG. 3 are intended as logical constructs; in practice, each sub-systemmay be implemented with any combination of physical hardware and/orsoftware components. Each uplink beam and/or sub-band spectrum, forexample, may have one or more corresponding processing cards or “slices”associated therewith, with each of the various cards communicating overa common backplane bus. Such an embodiment is described below inconjunction with FIG. 4. Alternatively, the various functions andchannel assignments may be shared between various cards, modules orcomponents in a wide array of alternate embodiments.

[0037] Channelizer 302 includes any digital circuitry and/or softwaremodules capable of receiving a digital representation of the sub-bandspectrum received on an uplink beam 204 and of dividing the sub-bandspectrum into any number of equally or unequally sized frequency‘slices’ 310. Slices 310 are also referred to herein as “packets”because time or code division multiplexed information segments withinthe slices may be readily routed independently of the other slices andsegments in the sub-band spectrum, as described below. In variousembodiments, digital channelizer module 302 is implemented with anapplication specific integrated circuit (ASIC). Exemplary ASICs formedusing complementary metal oxide semiconductor (CMOS) technologies andthe like are available from International Business Machines of Armonk,N.Y. and others.

[0038] Switch matrix 304 is any hardware and/or software structurescapable of directing frequency slices 310 between various ports 312 asappropriate. In various exemplary embodiments, switch matrix 304 isimplemented with one or more switch ASICs associated with each sub-bandor processing card, with each ASIC within matrix 304 beinginterconnected by a shared bus or other communications medium asdescribed below. The Various ASICs may be custom-built integratedcircuits, for example, or may be fabricated from field programmable gatearrays (FPGAs) that have been suitably programmed to store and/orforward digital data as appropriate within switch matrix 304.

[0039] Ports 312 are any hardware or software constructs (e.g. memorylocations, bus addresses, Unix-type socket ports, or other physical orlogical constructs) capable of receiving frequency slices 310 forsubsequent processing. Switch matrix 304 may provide for in-beam and/orcross-beam point-to-point, multi-cast and/or broadcast switching. In theexemplary embodiment shown in FIG. 3, for example, frequency slice 310Ais shown directly mapped to port 312A, which is associated with the samesub-band spectrum 204 as slice 310A. Alternatively, one or more slices310 may be mapped to ports 312 associated with one or more other beams204. FIG. 3 shows slice 310B mapped to ports 312B for an in-beammulti-cast, for example, with slice 310C mapped to multiple ports 312Con different beams to show an example of cross-beam multicasting.Because such switching is performed digitally, little or no signaldegradation typically results.

[0040] Regeneration module 308 is any hardware and/or softwareconstruct(s) capable of further processing the digital data encodedwithin the various frequency slices 310. In an exemplary embodiment,such processing is executed by one or more fixed ASICs or programmablechips 314 embedded within payload 300. Because the frequency slices 310are already processed digitally by the channelizer, the various bitstreams encoded within each slice 310 may be economically demodulated,further processed and remodulated prior to transmission using anyappropriate algorithms or techniques, without major duplication ofexpensive sampling and filtering functions. This synergy betweenchannelized and regenerative architectures enables both types ofprocessing to share overlapping functionality and to coexist, withoutrequiring the total duplication of circuitry that casual inspectionmight suggest. Types of digital processing that may be performed includeaccess verification, encryption, code division multiplexing (e.g. CDMA),data regeneration (i.e. recovery of corrupt or unclear data),compression, packet switching and/or any other data processing.Demodulation/remodulation may take place at any point during thechannelizing/routing process, and remodulation need not take placeimmediately following any processing handled by regeneration module 308.Demodulated data may be channelized and/or routed prior to remodulation,for example, or otherwise processed as appropriate. In the exemplaryembodiment shown in FIG. 3, for example, a frequency slice 310E is shownrouted to a port associated with an optional programmable modulator 314Bassociated with another beam 204B for processing.

[0041] Combiner module 306 is any hardware and/or software constructscapable of re-assembling the various frequency slices into new sub-bands216. After the frequency slices 310 are routed to the appropriate ports312 and/or otherwise processed as desired, data received at the variousports 312 associated with each downlink beam 216 are suitably combinedprior to re-transmission. The re-combined sub-bands are converted toanalog signals that can be transmitted on a downlink antenna 315 bydigital-to-analog converters (DACs) 316.

[0042] In operation, then, digital transponder unit 202 suitablyreceives sub-band spectra from the various uplink beams 204, divides thesub-band spectra into frequency slices that can be individually routedacross the various beams, provides any desired additional processing(e.g. signal reconstruction, encryption, etc.) and recombines thevarious slices to create new downlink beams 216. The overall capabilityof unit 202 is greatly enhanced through the additional digital signaland data processing that can be performed on digitized signals and datapackets. Further, the effective bandwidth of system 300 is greatlyincreased in comparison to similar analog circuit-based systems by theefficiency with which user signals and data can be packed together tofit into available bandwidth with minimum unusable segments. This isbecause signals and data can be processed in relatively small segmentsrather than in fixed-sized end-to-end circuits. The overall efficiencyof system 300 in terms of bandwidth, power consumption and other factorsis greatly enhanced, since demands for additional capability on one beam(or portion of a beam) 204 can be met with excess available capacityfrom the same or another beam.

[0043] With reference now to FIG. 4, an exemplary hardwareimplementation of a digital signal processing (DSP) payload 400 suitablyincludes a cabinet 402 housing various processing cards 404, 406 asappropriate. Cabinet 402 typically includes any number of slots forreceiving the various cards as well as a backplane bus to facilitatedata transfers between components on separate cards. Cabinet 402 mayalso have appropriate connects for providing electric power to each card404, 406.

[0044] Because different embodiments may incorporate any number ofprocessing cards, DSP payload 400 readily scales to implementations ofany size by simply adding or removing processing cards from cabinet 402.Various implementations may include, for example, any number oftransponder cards 404 as well as one or more resource management cards406. Redundant (“backup”) cards may also be provided in the event thatone or more cards should fail during operation. In one embodiment,cabinet 402 supports three active transponder cards 404 and a resourcemanagement card 406, as well as a backup transponder card and a backupmanagement card.

[0045] Each card 404, 406 housed within cabinet 402 suitably interfaceswith the backplane bus for inter-card data communications. Although anybus design could be used, exemplary embodiments may use industrystandard bus architectures such as the peripheral component interface(PCI) bus, VMEbus, or any of the other buses described in various IEEE,ARINC, MIL-STD and/or other commercial and/or military communicationsstandards. In one embodiment, the backplane bus is based upon amatched-impedance UNILINK switch fabric available from InternationalBusiness Machines of Armonk, N.Y.

[0046] The various transponder cards 404 operating with payload 400typically include one or more inputs capable of supporting one or moreinput channels as well as an interface to the backplane bus, suitableprocessing circuitry, and any number of outputs. In various embodiments,input and output slices with six or more 540 MHz input channels may beprovided, although other embodiments may have any number of channelsoperating at any frequency. Various embodiments may include any numberof input and/or output slices (e.g. 1-7 inputs and 1-7 outputs); thenumber of input slices need not match the number of output slices.Moreover, transponder cards 404 typically include a microcontroller,digital signal processor or other processor as well as a distributeddataswitch and associated circuitry for supplying power to the card.Although any processor could be used with the various embodiments, oneexemplary embodiment uses PowerPC 750 processors on both transpondercards 404 and resource management cards 408. Data processing for switchmatrix 304 (FIG. 3) and other functions may be shared between multiplecards 404, 406 to further improve redundancy and load sharing of system400.

[0047] Referring now to FIG. 5, an exemplary DSP payload 500 is shown inlogical form as including any number of channels 501A-n interconnectedby data switch 510. Each channel 501 generally corresponds to onesub-band spectrum received on an uplink beam 204, as appropriate. Anynumber of channels 501 may be processed on a common data processing card404 described above. Payload 500 also includes power supply 518,telemetry and command (T&C) processing 520 and clockgeneration/distribution 522 functions as appropriate. T&C processing 520and/or clock generation 522 functionality may be provided by one or moreresource management cards 406 (FIG. 4), or may be shared between one ormore data processing cards 404.

[0048] Each channel 501 suitably includes various modules for digitallyprocessing received signals. In the exemplary embodiment shown in FIG.5, the analog baseband signal received from the uplink antenna is firstfiltered and A/D converted at 502 to produce digital equivalents thatcan be further processed. As mentioned above, filtering and D/Aconversion may be handled within payload 500, or may be handled in aseparate D/A converter that can be located near the antenna to reducesignal noise, interference and other sources of error or distortion. Thedigital baseband signals may be further filtered 504 or otherwiseshaped/processed to obtain a desired digital sub-band spectrum, forexample. These digital signals may be demodulated at demodulation module506 as appropriate. Demodulator 506 suitably operates at variable ratesto accommodate different data types and protocols from varying datasources. The demodulated signals are then decoded, descrambled orotherwise processed 506 to a digital bitstream that can be packetized,routed and/or otherwise processed. Decoding module 508 suitablycommunicates with the T&C module 520, which gathers information aboutthe data and provides and command instructions to process the data asdesired. The demodulated data can be channelized and routed from anyinput port to any output port on payload 400. Switch 510 thereforeaccommodates switching and routing of individual packets and/or circuitsby mapping various slices of decoded packet data to one or more switchoutput ports, as described above in conjunction with FIG. 3.

[0049] Additional processing of the decoded data packets may take placebefore, during or after routing by switch 510. Examples of the varioustypes of processing that may be implemented includeencryption/decryption, access control/authentication, datacompression/extraction, protocol conversion, signal regeneration, errorcorrection and the like. Because the decoded data packets are simplysteams of digital bits, any type of processing can be performed on thedata prior to remodulation and D/A conversion. Such processing may becontrolled and/or carried out by T&C module 520 and/or by otherprocessors on any transponder card 404 or resource management cards 406(FIG. 4).

[0050] After digital processing and routing, the various digitalpackets/slices are recombined and formatted 512 as appropriate. Therecombined packets can then be encrypted, coded, multiplexed,re-modulated or otherwise processed by module 514 prior to transmissionon a downlink beam. DSP payload 500 may also include filtering and D/Aconversion capability 516, or D/A conversion may take place in closerphysical proximity to the downlink antennas to reduce noise, distortionand the like.

[0051] Additional detail of an exemplary implementation of a digitalpayload 600 having three multi-port DSP processing slices 406A-C isprovided in FIG. 6. With reference to FIG. 6, digital payload 600suitably includes any number of DSP slices 406, each of which include anADC 604, a channelizer 608, a digital switch fabric 622, a digitalcombiner 610, and a DAC 612, in addition to an optional regenerationmodule 616. Each slice 406 also includes power circuitry 618 forproviding electric power to the various slice components as appropriate.As described above in conjunction with FIG. 3, each of the various dataprocessing components may be implemented with application-specificintegrated circuitry, or with any other combination of hardware and/orsoftware.

[0052] As described above, each processing slice 406 receives sub-bandspectra or other input signals from an uplink antenna. In FIG. 6, thesesub-band spectra are shown as 560 MHz frequency bands provided in groupsof four bands at an input port 602, although other embodiments mayprocess different numbers of channels and/or channels of varyingbandwidths. Each of the input signals are received at slice 618, wherethe signals are converted to digital equivalents by ADC 604. Thesedigital equivalents may be provided in any manner to a channelizercircuit 608. In the embodiment shown in FIG. 6, digital equivalents areprovided via 8-bit parallel data connections, although alternateembodiments may use any level of bit resolution transmitted over anyserial and/or parallel connection. The channelized digital bit streamsare routed by various switching circuits 622 interconnected by backplanebus 620/624. As shown in FIG. 6, a UNILINK-type data bus couples thevarious switch ASICs 622 in a series of cascading logical rings, withdata transfers occurring in a linear fashion via switch interconnections624 and return bus 620. In alternate embodiments, the various switchASICs 622 may be interconnected in any mesh, web, star, linear, ring orother manner. Switched frequency slices 310 are then recombined at ASICs610 and/or digitally processed by regeneration ASICs 616 as appropriate.The recombined signals may then be D/A converted 612 and provided to thedownlink antennas via output ports 614 as appropriate.

[0053] Using the structures and logical constructs shown in FIGS. 2-6,digital payloads of varying capabilities may be readily fashioned.Referring again to FIG. 2, one embodiment of digital payload 202provides routing and data reconstruction functionality, as well asoptionally adjusting output power, providing for output linearization,adjusting output power and/or monitoring traffic and/or bandwidthutilization within payload 202. Output linearization, for example, maybe provided by pre-compensating data provided to the downlink beams fordistortion observed during the downlink transmission. Thispre-compensation may be programmably modified on-orbit in response toactual distortion observed, ground weather conditions, and/or otherfactors. Similarly, output power of the various downlink beams can beprogrammably adjusted upwardly or downwardly as needed to compensate forweather changes, evolving technologies, or other factors.

[0054] With reference now to FIG. 7, a further embodiment 700 of digitalpayload 202 suitably provides enhanced modular data handling capabilityas appropriate. Such data handling capabilities are typically processedor controlled by regeneration module 308 (FIG. 3) and/or T&C processor520 (FIG. 5). Because the various digital frequency slices 310 (FIG. 3)can be demodulated to extract a raw bit stream, digital payload 202 hasaccess to the channelized signals, thereby allowing the signals to beprocessed and manipulated to implement additional features not readilyavailable in the satellite environment. Examples of data handlingcapabilities include packet switching with additional queuing, forwarderror correction (e.g. using checksum, CRC, digest or other errorcorrection techniques), code based multiplexing (e.g. code divisionmultiple access (CDMA)), and/or enhanced security through userauthentication, access authorization, data encryption and/or the like.Examples of enhanced security include network registration and/or accesscontrol using digital credentials (e.g. passwords, digital signatures orthe like).

[0055] In an even further embodiment, the digital signal processingcapabilities of payload 202 can be expanded to incorporate direct beamforming, essentially creating an all-digital satellite payload 800 asshown in FIG. 8. Such embodiments typically do not require downconvertor output multiplexing capabilities, since the digital payload 202 isable to directly interoperate with phased array and/or other antennas toprocess uplink data and to form downlink beams ready for transmission.In such embodiments, digital payload 202 receives the analog basebandsignals from the input amplifiers 206, and provides output signals tooutput amplifiers 802 in analog form. Output amplifiers may be solidstate power amplifiers (SSPAs) or any other suitable amplifiers. Becauseall of the data processing is handled digitally within payload 800,significantly enhanced capabilities such as direct point-to-pointrouting, transmit power and coverage optimization, anti-jammingfunctionality (e.g. nulling) and the like.

[0056] Nulling, for example, typically involves detecting a hostilesignal at the antenna and instantly countering with a “null” signal tominimize the energy of the hostile signal as compared to friendlysignals. Because digital payload 202 is able to form individual downlinkbeams and to adjust the power of the output beams, nulling functionalitycan be directly implemented within payload 202 by creating a desireddownlink signal that can be directed at the hostile source. Moreover,hostile signals can be digitally extracted from uplink signals received,and/or access restrictions can be used to further secure datatransmissions within payload 202.

[0057] The architecture described above provides a platform fordesigning, building and operating satellites and to tailor theperformance of such satellites to specific applications desired. Bothbeam coverage and frequency, for example, can be made variable andchanged on-orbit. Moreover, both channelized and regenerativefunctionalities are made available, and these functionalities can beenhanced or changed while the satellite is in orbit. Still further, theflexibility designed into the system allows a high degree of frequencyreuse while maintaining full communications flexibility.

[0058] Because various payload resources (bandwidth, power, etc.) can bereadily monitored and adjusted on-orbit in real time within digitalpayload 202, for example, new techniques for exploiting the payloadresources are enabled. As mentioned above, bandwidth and other resourcesmay be monitored (e.g. by telemetry and command module 520 in FIG. 5 orthe like) to re-assign excess resources to other beams, channels orslices having a need for such resources.

[0059] With reference now to FIG. 9, an exemplary process 900 forre-allocating resources within the payload 202 suitably includes thebroad steps of defining an initial allocation (step 902), monitoringresource usage (step 904), and adjusting resource allocation upwardly(steps 906 and 908) or downwardly (steps 910) as needed. While FIG. 9refers to bandwidth as the particular resource being allocated, variousequivalent embodiments will allocate other resources such as electricalpower, antenna coverage and the like.

[0060] Process 900 begins with an initial allocation of satelliteresources (step 902). The initial allocation may be based uponhistorical or simulation data, previous iterations of process 900,experimental data and/or any other factors. Resource usage is thenmonitored (step 904) across the various links, channels, slices or otherrelevant resources to identify excess capacity (step 910) orover-utilized capacity (step 906). In the case of bandwidth, forexample, some or all of the channels can be monitored to identifyparticular channels with bandwidth utilizations above or below certainthreshold values. The particular threshold values used may be determinedexperimentally or from historical data, or may be otherwise determinedin any manner. Alternatively, the actual or estimated resourceutilizations of various channels may be maintained in a table or otherdata structure. Excess capacity identified in one or more under-utilizedchannels (step 912) may then be re-assigned for use by over-utilizedchannels (step 908), as appropriate. Conversely, channels that areneither over nor under-utilized may not be affected (step 914). Process900 shown in FIG. 9 is intended to be primarily conceptual; in practice,any resource monitoring and re-allocation process could be used in awide array of alternate embodiments.

[0061] The concept of on-orbit resource re-allocation enables variousnew business methods for bandwidth-provider organizations. Customers canbe offered variable bandwidth services, for example, that are moreuniquely tailored to the customer's actual needs than the “transpondercircuit” purchase model. Customers may be flexibly charged for actualbandwidth/transmit power consumed and geographical area covered, forexample, rather than paying for an inflexible “pipe” of fixed size andpower that may be over and/or under-utilized by the customer atdifferent times during the contract period. Alternatively, the “excess”or unused bandwidth and transmit power allocated to various circuitconnections may be reclaimed and used for other applications orcustomers.

[0062] Another process 1000 enabled by the flexible satellitearchitecture is shown in the data flow diagram of FIG. 10. Process 1000allows various parties to independently control a portion of thesatellite resources to thereby allocate the resources as desired. Withreference now to FIG. 10, a block of satellite resources 1002 is dividedand assigned amongst one or more resource managers 1006A-C who areresponsible for sub-assigning the resource to various entities 1008A-Coperating within the manager's domain. Although not shown in FIG. 10,the sub-entities may further sub-assign the resource to still otherentities (or multiple sub-levels of entities) in alternate embodiments.Managers 1006 may be battlefield commanders, for example, who assignsatellite bandwidth dynamically among units within their control. If aunit is assigned a fixed amount of bandwidth, for example, a commandermay temporarily assign a large portion of bandwidth to one unit (e.g. anunmanned aerial vehicle with a camera) for a short period of time toallow transmission of visual images, large data files or the like. Afterthe need for the bandwidth subsides, that bandwidth may be re-allocatedto other units for enhanced voice, data or other traffic. Suchflexibility may be particularly useful for network centric operations(NCO) and other military purposes, although the general concept could beused in corporate, industrial, entertainment or other governmentalsettings as well. Access control could be enforced within digitalpayload 202 (FIGS. 2-8) by assigning digital credentials (e.g.cryptographic certificates or the like) to the various managers 1006 andother entities 1008 and associating the various certificates with anaccess table or other data structure within payload 202 (e.g. within T&Cmodule 520 or the like). Numerous other allocation plans and techniquescould be formulated in a wide array of equivalent embodiments.

[0063] In various further embodiments (and with reference now to FIG.11), digital payload 202 can be combined with multi-beam phased array orsimilar antennas capable of projecting multiple spot beams to furtherenhance the flexibility of satellite 1100. In such embodiments,sub-frequency bands can be re-used on the multiple downlink spot beams1106, thereby improving bandwidth efficiency. One or more broadcastbeams 1104 may also be provided. These spot beams may be narrowlytailored and focused to provide bandwidth solely in desired areas, andmay also facilitate frequency hopping techniques that further enhancesecurity.

[0064] Accordingly, the overall efficiency of the satellite can bedramatically improved as the entire bandwidth (or other resources) ofthe satellite become available for use at all times during satelliteoperation. This effectively provides additional resource capacity thatcan be sold or leased, thereby significantly increasing the revenuestreams available from the digital payload. Moreover, the additionaldigital processing features (e.g. security, data regeneration, codemultiplexing and the like) further improve the usefulness and value ofthe satellite. Still further, the ability to re-configure the digitalpayload during design, manufacturing and/or on orbit provides even morevalue to customers by reducing the long-term risk of investment in suchtechnologies. Because the satellite can be reconfigured on orbit totransmit, receive and process beams at any frequency and carrying anytype of data waveforms, the architecture allows for a wide array ofapplications and a much longer product life than was previouslyavailable.

[0065] While at least one exemplary embodiment has been presented in theforegoing detailed description, it should be appreciated that a vastnumber of variations exist. Although various aspects of the inventionare frequently described in conjunction with a communications satellite,for example, the various techniques and systems described herein couldbe readily implemented in other contexts, including aviation, automotiveor maritime communications, cellular or other types of terrestrialcommunications, or in any other environment. It should also beappreciated that the exemplary embodiment or exemplary embodiments areonly examples, and are not intended to limit the scope, applicability,or configuration of the invention in any way. The foregoing detaileddescription will provide those skilled in the art with a convenient roadmap for implementing the exemplary embodiment or exemplary embodiments.Various changes can be made in the function and arrangement of elementswithout departing from the scope of the invention as set forth in theappended claims and their legal equivalents. The various steps of themethods, processes and techniques described in the appended claims couldbe practiced in any temporal order, for example, or may be practicedsimultaneously in various equivalent embodiments.

What is claimed is:
 1. A digital payload for processing a sub-bandspectrum received on an uplink beam at a communications satellite, thedigital payload comprising: a digital channelizer configured to dividethe sub-band spectrum into a plurality of frequency slices; a digitalswitch matrix configured to route each of the plurality of frequencyslices to at least one of a plurality of receiving ports; and a digitalcombiner configured to communicate with the receiving ports to receivethe plurality of frequency slices and to re-assemble the plurality offrequency slices to thereby form a plurality of output sub-bands fortransmission on an output beam of the communications satellite.
 2. Thedigital payload of claim 1 further comprising a digital regenerationmodule configured to demodulate at least a portion of the sub-bandspectrum to extract a digital bitstream therefrom, to digitally processthe bitstream, and to remodulate the bitstream after processing.
 3. Thedigital payload of claim 2 wherein the digital regeneration module isfurther configured to digitally process the bitstream by performingerror correction.
 4. The digital payload of claim 2 wherein the digitalregeneration module is further configured to digitally process thebitstream by performing code division multiplexing.
 5. The digitalpayload of claim 2 wherein the digital regeneration module is furtherconfigured to digitally process the bitstream by performing accesscontrol.
 6. The digital payload of claim 2 wherein the digitalregeneration module is further configured to digitally process thebitstream by performing network registration.
 7. The digital payload ofclaim 2 wherein the digital regeneration module is further configured todigitally process the bitstream by performing cryptographic manipulationof the bitstream.
 8. The digital payload of claim 1 further comprising acontroller configured to monitor bandwidth consumption of the sub-bandspectrum and to adjust the bandwidth consumption in response thereto. 9.The digital payload of claim 1 further comprising a built-in testcircuit.
 10. The digital payload of claim 1 further comprising an analogto digital (A/D) converter configured to receive the uplink beam and toproduce the sub-band spectrum therefrom.
 11. The digital payload ofclaim 10 wherein the A/D converter is further configured to sample theuplink beam at an IF frequency rate.
 12. The digital payload of claim 1further comprising a digital-to-analog (D/A) converter.
 13. The digitalpayload of claim 12 wherein the D/A converter is further configured tooperate at an RF frequency rate.
 14. An all-digital payload forprocessing a plurality of sub-band spectra received on a plurality ofuplink beams at a communications satellite, the digital payloadcomprising: a digital channelizer configured to divide each of thesub-band spectra into a plurality of data packets; a digital switchmatrix configured to route each of the plurality of data packets to atleast one of a plurality of receiving ports; an embeddable digitalregeneration module in communication with the digital switch matrix,wherein the digital regeneration module is configured to demodulate atleast a portion of the plurality of data packets to extract a digitalbitstream therefrom, to digitally process the bitstream, and toremodulate the bitstream after processing; and a digital combinerconfigured to communicate with the receiving ports to receive theplurality of data packets and to re-assemble the plurality of datapackets to thereby form a plurality of output sub-bands for transmissionon an output beam of the communications satellite.
 15. A method ofprocessing a sub-band spectrum received on an uplink beam at a digitalpayload for a communications satellite, the method comprising the stepsof: digitally dividing the sub-band spectrum into a plurality offrequency slices; routing each of the plurality of frequency slices toat least one of a plurality of receiving ports; and digitally processingat least a portion of the frequency slices; and digitally re-assemblingthe portion of the plurality of frequency slices after processing tothereby form a plurality of output sub-bands for transmission on anoutput beam of the communications satellite.
 16. The method of claim 15further comprising the steps of converting the analog uplink beam to adigital representation of the sub-band spectrum prior to the dividingstep.
 17. The method of claim 16 wherein the converting step occurs atan IF frequency rate.
 18. The method of claim 15 wherein the routingstep comprises simultaneously routing at least a portion of theplurality of frequency slices to multiple receiving ports to therebyimplement a multi-cast function.
 19. The method of claim 15 furthercomprising the steps of monitoring the sub-band spectrum to identifychanges in bandwidth consumption and adjusting the routing step inresponse to the changes to thereby improve the efficiency of the digitalpayload.
 20. A satellite receiving a plurality of uplink beams andproducing a plurality of downlink beams, the satellite comprising: anuplink antenna configured to receive the plurality of uplink beams; adownlink antenna configured to produce the plurality of downlink beams;an analog-to-digital (A/D) converter configured to convert the uplinkbeams to digital uplink equivalents; an all-digital payload comprising:a digital channelizer configured to receive the digital uplinkequivalents and to divide the digital uplink equivalents into aplurality of frequency slices; a digital switch matrix configured toroute each of the plurality of frequency slices to at least one of aplurality of receiving ports; and a digital combiner configured tocommunicate with the receiving ports to receive the plurality offrequency slices and to re-assemble the plurality of frequency slices tothereby form a plurality of digital output sub-bands; and a digital toanalog (D/A) converter configured to convert the digital outputsub-bands to downlink beams transmitted by the downlink antenna.
 21. Thesatellite of claim 20 wherein the A/D converter is further configured tosample the uplink beams at an IF frequency.
 22. The satellite of claim20 wherein the D/A converter is further configured to sample the outputsub-bands at an RF frequency.
 23. The satellite of claim 20 wherein theuplink antenna is a digital beam-forming antenna.
 24. The satellite ofclaim 20 wherein the uplink antenna is a phased array antenna.
 25. Thesatellite of claim 20 wherein the downlink antenna is a digitalbeam-forming antenna.
 26. The satellite of claim 20 wherein the downlinkantenna is a phased array antenna.
 27. A digital payload for a satelliteconfigured to receive a sub-band spectrum via an uplink beam and toprovide a downlink beam, the digital payload comprising: a backplanehousing having a backplane bus; and a plurality of processing cards,each processing card comprising: a channelizer circuit configured toreceive the sub-band spectrum and to divide the sub-band spectrum into aplurality of frequency slices; a digital switch matrix comprising aplurality of switching circuits, wherein each of the plurality ofswitching circuits is configured to route a portion of the plurality offrequency slices to at least one of a plurality of receiving ports viathe backplane bus; and a digital combiner circuit configured tocommunicate with the receiving ports to receive the plurality offrequency slices and to re-assemble the plurality of frequency slices tothereby form an output sub-band for transmission on the output beam. 28.The digital payload of claim 27 wherein each of the plurality ofprocessing cards further comprises a regeneration circuit configured todemodulate at least a portion of the sub-band spectrum to therebyextract a digital bitstream therefrom, to digitally process thebitstream, and to remodulate the bitstream after processing.
 29. Meansfor processing a sub-band spectrum received on an uplink beam at acommunications satellite, the means for processing comprising: means fordividing the sub-band spectrum into a plurality of frequency slices;means for routing each of the plurality of frequency slices to at leastone of a plurality of receiving ports; and means for communicating withthe receiving ports to receive the plurality of frequency slices and tore-assemble the plurality of frequency slices to thereby form aplurality of output sub-bands for transmission on an output beam of thecommunications satellite.
 30. The means for processing of claim 29further comprising a means for digitally regenerating the sub-bandspectrum, wherein the means for digitally regenerating comprises meansfor demodulating at least a portion of the sub-band spectrum to extracta digital bitstream therefrom, means for digitally processing thebitstream, and means for remodulating the bitstream after processing.31. A method of allocating a satellite resource within a satellite, themethod comprising the steps of: performing an initial allocation of thesatellite resource; monitoring the allocation of the satellite resourceduring operation of the satellite to identify available portions of thesatellite resource and over-utilized portions of the satellite resource;and re-allocating the satellite resource during operation of thesatellite to re-assign the available portions of the satellite resourceto the over-utilized portions of the satellite resource.
 32. The methodof claim 31 wherein the satellite resource is bandwidth.
 33. The methodof claim 31 wherein the satellite resource is electric power.
 34. Themethod of claim 31 further comprising the step of adjusting a cost ofthe satellite resource associated with a customer in response to there-allocating step.
 35. A method of independently controlling a portionof a resource within a satellite, wherein the resource is consumed by aplurality of entities each having a digital credential, the methodcomprising the steps of: providing an allocation of the resource to aresource manager; receiving a sub-allocation of the resource among theplurality of entities from the resource manager; and associating thesub-allocation with the digital credentials received from the entitiesto thereby enforce the sub-allocation of the resource.